HELP,,, 3.31,3.55 or 3.73 for 2011-5.0-GT?

Discussion in '2010 - 2014 Specific Tech' started by Husker, May 22, 2010.

  1. The July Motor Trend mentions the GT with 3.73 rear end needs 3rd gear to hit 60 mph. It did so in 4.4 seconds but I bet the 3.55 car can hit 60 in the same amount of time as you won't need that second shift.

    Something else to think about.


  2. I don't get it. Whats the point of all the shifting if it doesn't accelerate? Why the extra shifts w/ 3.73?
  3. Go with 3.73s.They will be the perfect gear for the new 5.0. I have 2001 GT and at first I went with 3.73s and loved them but switched to 4.10s last year and like it even more. Also I'm putting down about 300rwhp (350 crank) with an automatic. I do a lot of highway driving and have no problems running at 2,600 RPM at 70mph. I still can get 23+mpg all highway.
  4. If the 3.55 allows 2nd gear to reach 63 mph whereas the 3.73 only allows for 59, you lose time having to shift to third gear with the 3.73 while the 3.55 is still in 2nd gear. This would only hold true for zero to 60 as opposed to zero to 65 but it demonstrates how closely spaced the gears are in the new 6 speed.

    Does anyone think a car with 400 ft/lbs of torque needs to hit 3rd gear before 60 mph? I remember a buddy of mine with an old Mazda was always shifting like a maniac. But that little inline four probably put out 120 ft/lbs max. Just sayin . . .


  5. LOL Thanks :)
  6. Hi Y'all...

    I just bought a 2011 GT Coupe with Brembo Package and 3.73's...thats it! I ordered the car and do not regret ordering it like this ONE bit. Someone was mentioning that the Brembo package isn't worth it. Are you kidding?? :) Have you priced out what brakes alone would be aftermarket? For $1600 you get a set of big 19x9's with sticky Pirellis, the big brakes and a very nice strut tower brace. Its definitely worth that money. Whether you drive on the street or road race (which I do both), the brakes grab harder, are more linear and have better feel especially at higher speeds.

    The 3.73's are great. Do you need them, eh, I don't know. I sell Fords, so I've driven the 3.31 car too and it needs a bit of time to rev out. I knew this engine was going to be more of a "revver" so the 3.73's help to keep the rpm up in the power band. The 3.55 car is a nice compromise. I drive mostly street, but out on the highway at 70 i'm barely turning 2000 rpm. I do start in 2nd sometimes and it pulls away from that with no hiccups. On the street, the 3.73's make the car scoot and lots of fun. If you're going to modify the hell out of your car, 3.55's or 3.31's are probably better so first gear doesn't go so quick. If you're going to do basic bolt ons (like me), get the 3.73's.
  7. Anybody have any actual 0-60 times with 3.73's vs. 3.31 ? I mean with the new 5.0 and the same tires? It doesn't seems like the new motor needs the extra help...
  8. Make the right comparison

    There are a lot of comparisons on here that do not help with the question, “What gears to get”. The gear choice is different for each car and setup. Even comparing a 2009 GT to a 2011 GT will yield different results based on gear selection and tire selection. Here is a link to my gear chart that will tell you what you need to know about RPMs and speeds based on gear selections for specific cars. Also, remember that the red line is different on the 2011.
    As far as Brakes go, GET THE BRAKE UPGRADE!!!

    Good luck with your research.
  9. The Brembo package is a good deal, and if you want the tires and wheels, or if you will be tracking the car, it is probably worth it.

    But, correct pad compound selection will work wonders. Brakes usually give up because the pad/rotor temp exceeds the MOT of the pad compound. Aftermarket pads solve this. Rotor warping has to do mostly with sitting (no moving) while hot. You get differential cooling of the rotor that is within the caliper versus the rest of the rotor.

    Really the only down side with aftermarket pads is that you can't have quiet, low dust, good cold bite and high MOT all in one package.

    Regarding the gears, I can only offer my experience with an '85 GT. Blew out the factory rear end, and put in a bigger one with 3.73's (IIRC). While it scooted better, I didn't like it for around town driving--more shifting.
  10. Don't forget the tires

    The tires on the newer Mustangs are usually 18" or 19". If you do the math these tire and wheel combinations on the newer cars are taller than the older Mustangs so you effectively lose gear ratio. I have 3.73 gears in my 2010 Mustang GT and it still seems a bit slow to wind up, but I average 18 to 19 mpg in mixed driving. A 2011 Mustang would benefit from a 3.73 gear greatly because of its higher 7000 rpm redline. This is the whole idea behind using small, high revving, good breathing engines to equalize the displacement difference of larger engines such as the 6.2L Chevy. The Chevy cannot rev. as high so it relies more greatly on it's torque to move the car. The Mustang generates good torque, but revs. higher and greater torque can be transmitted to the rear wheels through gearing and torque multiplication. Basically to determine RPM at a certain MPH or vice versa use this formulas:
    (Tire Height in Inches x 3.14) x [RPM / (Transmission Ratio for a given gear x Rear End Ratio] x [60min(in one hour)/5280ft(in one mile)] = MPH

    Tire Height = Rim Height + [2 x (Width x Aspect Ratio)]

    18" Rims
    P245/50R18 Tires
    3.73 gears
    .65 5th gear ratio
    RPM @ 70MPH

    1st Step : Tire Height = 18inches + [2 x (245mm x .50)] = 18inches + 245 mm --- 245mm/25.4(metric conversion for mm to inches)= 9.646inches --- 18inches + 9.646inches = 27.646inches

    70MPH x 5280ft(per mile) = 369600ft(per hour) x 12inches(per foot) = 4435200inches(per hr)/60minutes(per hour) = 73920inches(per minute)/[27.646inches(tire height) x 3.14(tire circumference)] = 851.5Revolutions(per minute at the tire) x [3.73(rear end ratio) x .65(transmission overdrive ratio)]= 2064.5RPM @ 70MPH
  11. I've got the 3.15s in my auto and I'm not wanting for more. I'm seeing 22-23 mpg with a moderate foot on a tight engine, so I expect to see 25 or so further on down the road. Not too bad for an engine that makes 413 hp, this is a daily driver after all so I don't want to do anything that sacrifices driveability.

    A set of 3.73s is only $175, it's not the end of the world if I ever wanted to swap them out. My pops has the 3.73s in his '10 GT and if he had to do it again, he'd rather not have them due to the extra shifting involved.
  12. Why not just get what it comes with and swap out if you don't like? I've seen other posts around with loss of mpg because of higher gears. Also saw complaints of first gear being useless. The gear ratio with six speed and all that power should allow stock gears to work great. Even the auto in the test drives beat the cameras and stayed up with the gear swapped six speeds.
  13. My experience with 3.73s:
    highway mpg 23 @ 70 mph
    mixed highway and rough city traffic 19mpg

    I shift 1st to 4th to 6th around town so no extra shifting needed. I have no problem just leaving it in 6th from about 40 mph even with hills etc.

    So IMHO, go for the 3.73s unless you do a whole lot of highway driving and gas money is an issue (a few mpg over a few years can really add up when your putting in premium).